DBK,
Been using it for years. Started with conventional saltwater reels, then moved to salt water fly reels and now use it on even my smallest trout fly reels. It solves several problems and creates a few others. Because of its small diameter it can greatly increase the amount of backing a reel will hold. It can make a 50wide conventional behave like an 80wide. It 's great on large arbor fly reels which frequently have low backing capacity. On trout size fly reels (like the smallest orvis/hardy) it allows you enough backing to have piece of mind for the rare run into the backing. On the downside this stuff is expensive. However since it doesn't dry rot it can far outlast normal backing. Its small diameter can be misleading. Using too small a diameter can allow the line to slip between spool and sideplate and other places it shouldn't go because it has virtually no stiffness or memory. On a final note this stuff will cut you like a buzzsaw if a fish runs into your backing at speed and you get your fingers on it. Afterall, most of it is made of some type of kevlar! Still, keeping in mind the downsides, I use it extensively.

Thanks 501. I have about 80 yards left on a 500 yard spool. I saltwater fish on St. George Island and use the stuff exclusively (spin fishing). I have been buying my PowerPro in the 1500 yrd spools for around $80 off of Ebay. My first trip to the bay broke me from using mono on the oyster bars. The stuff is worth every dime if you have ever had a Jack cut across a bar.

I was thinking it would work but I had concerns that the braid might "cut" the spool.

DBK,
A few additional thoughts. Braided line is very slick and abrasive. When installing it on the reel, either put down a couple of layers of masking tape first or a few feet of monofilament (then knot the braid to the mono). Otherwise the braid may slip on the spool. There are also many who believe that braid can actually leave a groove or cut on a line guide that sustains a long run. These may eventually damage your fly lines and leaders. On larger rods roller guides eliminate this. On my larger fly rods I use either silicon carbide or titanium guides which are harder to prevent this. Snake guides are available in a titanium coating. Usually on my small weight trout rods I just use regular snake guides with silicon carbide stripper guides as long sustained runs are kind of rare. Braid will also cut into itself on the spool under pressure. The way to beat this is to use a powered line winder and load the reel with braid under a lot of tension. As braid has almost no stretch this is safe. Don't ever load mono under a lot of tension as it stretches and can explode a spool made of cheap metal. I frequently use both masking tape and mono when loading a reel with braid. Be careful with the knots used as many will slip right out with braid. I always superglue my knots and check them for sturdiness. Hope this helps.

I am being a little over cautious about the braid cutting the spool. The truth is that I upgraded my reel to get a better drag. I had a large fish get off last year because my cheap fly reel locked during a run. Fish snapped the 6x and I was crushed. I am doing the upgrades for that 1 in 200 fish that needs to be "put to reel".